Cathode ray tube with matrix forming elemental electron beams and means for selectively forming them into characters at the face plate of the tube

ABSTRACT

A character generator electric discharge tube for selectively switching elemental portions of an electron beam. With the use of accelerating cylinders and spirals between the electron gun and the electromagnetic focus coil, a considerable reduction in the length of the tube is effected.

United States Patent [72] Inventors Arthur T. Starr New Bar-net; Peter F. T. 'C. Stillwell, Crookham Village, England [21] Appl. No. 695,626 [22] Filed Jan. 4, 1968 [45] Patented Feb. 16,197] [73] Assignee Zerox Corporation Rochester, N.Y. a corporation of New York [54] CATIIODE RAY TUBE WIT II MATRIX FORMING ELEMENTAL ELECTRON BEAMS AND MEANS FOR SELECTIVELY FORMING TIIEM INTO CHARACTERS AT THE FACE PLATE OF THE TUBE 6Chims,5l)rawing Figs. [52] U-S. 313/77, 313/80, 313/86 [51] Int. Cl. -H0lj 29 74; 1101129/46 so l ield ol'Search 313/83, 77, 86 [56] References Cited UNITED STATES PATENTS 2,824,250 2/1958 McNaney et al 313/77 2,862,144 11/1958 McNaney 3 I 3/86X 3,143,681 8/1964 Schlesinger 313/83 3,198,976 8/1965 Starr 313/86 3,286,114 11/1966 Schlesinger 313/83 Primary Examiner- Roy Lake Assistant Examiner-V. Lafranchi Attorneys-Ronald Zibelli, James J. Ralabate and Norman E.

Schrader ABSTRACT: A character generator electric discharge tube for selectively switching elemental portions of an electron beam. With the use of accelerating cylinders and spirals between the electron gun and the electromagneticfocus coil, a'considerable reduction in the length of the tube is effected.

PAIENTED FEB? s IQYi sum 2 or 2 FOCUS con.

INVENTORS ELL RL m g T 0 7 T T. A m mm T AP Y B CATHODE RAY TUBE WITH MATRIX FORMING ELEMENTAL ELECTRON BEAMS AND MEANS FOR SELECTIVELY FORMING THEM INTO CHARACTERS AT THE FACE PLATE OF THE TUBE BACKGROUND OF THE INVENTION In US. Pat. No. 3,198,976, entitled ELECTRIC DISCHARGE TUBES AND APPLICATIONS THEREOF, to Arthur T. Starr, there is disclosed an electric discharge tube including beam switching means interposed in the path of the electron beam for selectively switching elemental cross sec tions of said beam either simultaneously or consecutively whereby elemental beams may be caused to emerge from said switching means in a spacial arrangement or pattern determined by input signals.

The beam switching means is in the form of an electron impervious member provided with an array of apertures, each ringed by a conductive annulus to which a connection may be made from without the tube. The electron impervious member preferably defines at least one matrix of apertures forming an array of rows and columns. Each matrix may be formed by punching apertures in a plate of dielectric material, such as mica, and laying around each aperture, on either side of the plate, a conductive annulus provided with a lead by any convenient technique, such as metal evaporation under vacuum or printed circuit or photoetching techniques.

The foremost application of the cathode ray tube disclosed in the above set forth patent, is the visual display of graphic data upon a fluorescent screen in a cathode ray tube configuration, the data being, for example, alphanumeric information presented to a predetermined area of a fluorescent screen so as to excite therein a visual display of said selected character. However, it has been found that the tube, known in the art as a Matricon tube, is inconveniently long, if the height of the character on the tube face is to be much smaller than the apertures in the matrix array. The undue length of the Matricon tube does not lend itself, therefore, to a compact and inexpensive system utilizing the tube.

OBJECTS It is, accordingly, an object of the present invention to provide an improved electric discharge tube.

It is another object of the present invention to shorten the length of an electric discharge cathode ray tube for use in a character generation and display system.

It is another object of the present invention to provide a more compact and efficient cathode ray tube utilized for the presentation of alphanumeric characters on the face thereof.

BRIEF SUMMARY OF THE INVENTION In accomplishing the above and other desired aspects, Applicants have invented new and improved apparatus for reducing the length of an alphanumeric character generation cathode ray tube. The conventional cathode ray tube comprises cathode, accelerating and focusing anodes, deflection means, and a phosphorescent or fluorescent layer on the face of the tube for the emitting of light by presentation of the electron beam for visual recognition. The present invention provides for the inclusion of cylindrical and spiral (helical) arrays for allowing the electron beam to travel through regions of lower potential before the beam meets the focusing field prior to presentation to the face of the tube. By utilizing this technique, the length of the tube can be made appreciably shorter, sometimes as much as by a factor of half the length.

DESCRIPTION OF THE DRAWINGS For a more complete understanding of the invention, as well as other objects and further features thereof, reference may be had to the following detailed description in conjunction with the drawings wherein:

FIG. I is a cathode ray tube embodying a beam switching matrix;-

FIG. 2 illustrates a beam switching matrix utilized in the tube illustrated in FIG. 1;

FIG. 3 is a side view of the tube similar to that of FIG. I incorporating the principles of the present invention;

FIG. 4 is a representative diagram of the cathode ray tube of FIG. 3 and associated dimensions;

FIG. 5 is a representative diagram of the voltage gradiant and electron path of the cathode ray tube shown in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 of the subject application, which is the same figure as appears in the above set forth US. Pat. No. 3,198,976, illustrates a cathode ray tube 1 comprising, successively spaced, a cathode 2, a control grid 3, a beam switching matrix 4, a first anode 5, a post deflection accelerator anode 6, and a receiving means 7, for such of the elemental electron beams as are passed through the matrix 4. Such receiving means may be an array of target electrodes or a dielectric member of an electrostatic storage device or a fluorescent screen. The cathode, which is heated by filament 8, provides a beam of electrons of adequate cross section to, flood the operational area of the beam switching matrix 4. Deflection and focusing coils 9 are located around the neck of the tube. Deflection plates within the tube could, however, take the place of the deflection coils.

In FIG. 2 a beam switching matrix 4 according to the present invention comprises a plate of dielectric material, such as mica, having an operational area of, for example, 0.3 inches by 0.4 inches, provided with apertures, such as at 10, extending some 0.02 inches across and arranged in a rectangular array of 9 rows and 7 columns, each aperture being ringed by a conductive annulus, such as 11, complete with lead 12 to which an electrical path is extended from without the cathode ray tube when the matrix is mounted therein.

A beam of electrons is caused to issue from cathode 2, in FIG. 1, so as to flood the operational area of matrix 4, control grid 3 being kept at a suitable potential to enable this action. Assuming in the first instance that none of the conductive annuli are connected to a voltage source, the impinging electrons filter through the apertures and emerge in elemental beams which conform to the apertures both in number and spacial arrangement. The elemental beams, accelerated by the first anode 5 fed with a positive potential of conveniently high value, are prevented from spreading out by the focusing coil, denoted at 9, and are deflected in parallel formation onto a given area of the screen 7 in accordance with suitable X and Y deflection waveforms made. available at the deflection coils also denoted at 9. The elemental beams impinging upon the fluorescent screen 7 excite therein an array of light dots which is a replica of the array of apertures.

Assuming that at a given area on screen 7 it is desired to produce a display of the capital letter I as styled, the elements of the matrix 4 are so biased that only the apertures along the longitudinal axis of the matrix and those immediately adjacent thereto at either longitudinal end allow the impinging beam to pass. The result of this action is a dotted display of said letter. By suitable selection of the elements and the provision of suitable deflection waveforms, a wide and variable range of graphical data may be selectively displayed upon the screen in any desired spacial interrelation.

The dimensional aspects of the system described in conjunction with FIGS. 1 and 2 is seen in FIG. 4. It is thus seen that the length of the tube itself is given by L u v 2" (for the gun) v+v+2' In practice the character height h and the length v are given,

the latter being determined mainly by consideration of focus and deflection. For example, the Matricon tube disclosed in the above set forth U.S. Patent, v 10 inches, h is desired to be 0.05 inches, and a very small aperture is at least 0.1 inches. It follows that the tube is over 30 inches long, which is not convenient, as hereinbefore set forth.

In order to shorten the tube any substantial amount, it is possible to reduce the size of the matrix apertures, but this reduces the current and corresponding brightness as well as posing a difficult problem of construction. The present invention arose out of the observation that, if an accelerating spiral is used between the electron gun and the final anode cylinder, then the relation is in fact replaced by the relation The present invention disclosed how design arrangements can be made for which l E F h s) when F is a reduction factor, which can be as high as 4 or more. Since u is the major contribution to the length of the tube, a considerable reduction is the length may be made without making very small matrix apertures.

The invention consists of choosing a suitable potential distribution between the electron gun and the magnetic focus lens. In FIG. 5 there is a matrix AC of height H, a magnetic lens centered at O, and a character of height h at a distance v from the focus coil. If it is assumed that the potential to the right of the focus coil is a constant V,,, then the paths of electrons in this space are straight lines, as shown. Shown are the axial rays A08 and the outside ray COD.

At any point of the ray COD the electrons will have a transverse velocity q and a longitudinal velocity q. If it is assumed that there is a potential distribution v along the longitudinal (x) direction, then q, is constant a n d q k /Vln particular at the central point 0, Q Q 0 K V It follows that The time T taken for the electrons to travel from C to 0 is given by H q T, since the electrons have a constant transverse velocity q and it transverses a transverse distance H in this time. Therefore But in this time the electron travels a longitudinal distance u with a velocity which is q k V at distance x. it follows that Therefore u d hvq T 0 *q 3;

H u V0 I I) J;) V dZ. This is the fundamental equation of the system. If V= V the usual equation l is obtained namely H I v=u The fundamental equation can also be obtained by electron optics using Snells Law: n sin 0 constant, and taking n as proportional to the velocity of the electron, i.e., n ass/V This is because the electron velocity is the group velocity, which is inversely proportional to the phase velocity.

If there is a potential distribution V, from 0 to X,, V from x to x,+x and V, from x,+x to x,+x +x =u,then

H x1 V0 x? V0 13 V0 4W n V1 da:+j; dz+ x2 dx. (6k

where u x, x, x Thus, the contributions to H/h v can be calculated separately and added. It follows then that for a constant potential gradient, V,,/N, that Referring now to FIG. 3, disclosing the apparatus of the present invention, like means are designated the same as that exists in FIG. 1. Between the aperture matrix 4 and the focusing coil 9 is the apparatus which included in the tube envelope results in a considerably shorter overall tube with the same size viewing face. That is, cylinder electrode 31 is placed between the spiral 32 and the magnetic focus coil 9. External wire connections are not shown in this figure so as not to complicate the figure with extraneous material.

As a general case, if there is a cylinder or tube of potential V,,/N for the length d u, a spiral of length d u, and a cylinder or tube of potential V, of the remaining length l d, d )u, then by equation (6) the reduction factor F is In the case where d 0.4 d and d 0.2,

Thus, where the voltage gradient N is 10, then F equals 2.07. Where the voltage gradient N is 20, then the reduction factor F20: 2.63-

As a specific example, if the tube envelope is 7 inches in diameter and 42 total deflection angle, then the distance v 10.5 inches. Let the matrix height H 0.214 inches where each of the matrix apertures is 0.02 inches at 0.03 inches spacing. If the character height h 0.08 inches i.e. 75 characters along 6 inches; with the use of a low potential cylinder at 0.5 u, a spiral for 0.311 and a high potential cylinder of 0214, then if there is a voltage gradient N= 15 (l to 15 KV), then utilizing equation 9 the improvement factor F 2.6. Then u (0.2l4/0.080l0.5/2.6) 10.8 inches, and the tube is 23 inches long. Thus, the first cylinder anode would be 5.4 inches long, the spiral anode 3.3 inches long, and the second cylinder anode 33 2.2 inches long. This is'a very convenient and practical solution and reduces the length of the tube by almost l0 inches.

If H =0.2l4 inches and H =0.050 inches characters along six inches), then for the same configuration u =l7.3 inches and the tube is 30 inches long. The tube is slightly shorter than the present tube, but can use a matrix with twice the linear dimensions with the light output multiplied by at least a factor of four. The cylinders, as described herein, could have cross-sectional shapes other than a circle where the situation requires it.

When the electrode voltages are chosen, however, to give a substantial image reduction, it has been found that for a reduction in image aberration a mesh electrode 34 may be inserted at the junction of the low voltage cylinder 31 and the spiral electrode 32. Without this electrode mesh, the paths of electrons emanating from the cathode 2 are caused to crossover, i.e., form an image of the cathode 2, just inside the spiral electrode 32. This is due to the fact that the lateral components on the electron beam are substantially increased by the curved fields. Secondary emission from the meshielectrode 34 can be limited by treating the electrode by any of the known techniques, with the addition of further electrodes selectively arranged to collect any secondary electrons, depending on the tube size.

In the foregoing, there has been disclosed improved apparatus for shortening the length of a character generation cathode ray tube. While the present invention has been described in conjunction with the Matricon tube as disclosed in U.S. Pat. No. 3,198,976, the invention is not limited thereto but may be extended to be used in any cathode ray tube-where a plurality of electron beams must be presented in parallel type arrangements. In addition, the numerical values given as examples for the size of the tube are exemplary only and other size tubes may be altered in conjunction with the principles of the present invention. Thus, while the present invention, as to its objects and advantages, as described herein, has been set forth in specific embodiments thereof, they are to be understood as illustrative only and not limiting.

We claim: 1. An electric discharge tube comprising: a face plate; a two-dimensional matrix of apertures in an electron impervious member; electron emitting means for generating an electron beam of adequate cross-sectional area to flood said matrix;

an individual conductive annulus around'each aperture and having an individual lead extending to the outside of the tube for the selective application thereto of a beam switching potential; and first, second, and third anodes spaced-apart along the axis of said tube between the matrix and the face plate of the tube for accelerating elemental electron beams defined through said apertures, wherein said first anode is a cylinder, said second anode is a spiral, and said third anode is a cylinder, respectively, and positioned in that order. 2. An electric discharge tube comprising: a face plate; a source of emitted electrons; aperture means for forming said emitted electrons into a plurality of elemental beams; first, second, and third electrode means spaced-apart along the axis of said tube between the aperture means and the face plate of the tube for accelerating said electrons; and means for focusing said electrons on a selectable portion of the face of said electric discharge tube, said focusing means being positioned adjacent said third electrode means along said axis of said tube, wherein said electrode means are positioned between said aperture means and said focusing means to accelerate said electrons through said electrode means, said first, second, and third electrode means comprising a cylinder, spiral, and cylinder respectively, and positioned in that order. 3. The electric discharge tube as set forth in claim 2, wherein the lengths of said first, second, and third electrode means are calculated according to the relationship:

Where in, x x are the lengths of the cylinders, spiral, and cylinder,

respectively. v is the voltage at said focusing means, v,, v v;, are the voltages at said cylinder, spiral, and

cylinder, respectively, and u is the sum of x, +x +x 4. The electric discharge tube as set forth in claim 2 wherein the improvement factor in reducing the length of said cathode ray tube by the use of said first, second, and third electrode means is calculated according to the relationship:

a source of emitted electrons; aperture means for forming said emitted electrons into a plurality of elemental electron beams;

first, second, and third electrode means spaced-apart along the axis of said tube between the aperture means and the face plate of said tube for accelerating said elemental electron beams;

means for focusing said elemental electron beams on a selectable portion on the face of said cathode ray tube, said focusing means being positioned adjacent said third electrode means along said axis of said tube;

means for individually selecting the electron beams to pass through said aperture means, wherein said electrode means are positioned between said aperture means and said focusing means to accelerate said electrons through said electrode means;

said first, second, and third electrode means comprising a cylinder, spiral, and cylinder, respectively, and positioned in that order.

6. The electric discharge tubes as set forth in claim 5 further including:

mesh electrode means at the junction of said first and second electrode for reducing image aberration due to electron crossovers along the axis of said tube at predetermined electrode potentials.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3,564,319 Dated February 10, 1971 Inventor(s) Arthur T. Starr et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 2, line 17, after "cylinder", second occurrence, insert a comma Claim 3, second column, lines 1 and 2, after "dx delete the period and insert a comma;

Claim 3, second column, line 3, delete "Where" a: insert where-;

Claim 3, second column, line 4, delete "cylinder and insert cylinder-;

Claim 3, second column, line 6, delete "v and insert V 7 Claim 3, second column, line 7, delete "v v and insert -V V V Claim 6, line 1, delete "tubes" and insert tub Claim 6, line 4, delete "electrode" and insert electrodes.

Signed and sealed this 29th day of June 1971.

(SEAL) .Attest:

[EDWARD M.FLETCHER,JR. WILLIAM t2. SGHUYLER, JR Attesting Officer Corunissioner of Patents 

1. An electric discharge tube comprising: a face plate; a two-dimensional matrix of apertures in an electron impervious member; electron emitting means for generating an electron beam of adequate cross-sectional area to flood said matrix; an individual conductive annulus around each aperture and having an individual lead extending to the outside of the tube for the selective application thereto of a beam switching potential; and first, second, and third anodes spaced-apart along the axis of said tube between the matrix and the face plate of the tube for accelerating elemental electron beams defined through said apertures, wherein said first anode is a cylinder, said second anode is a spiral, and said third anode is a cylinder, respectively, and positioned in that order.
 2. An electric discharge tube comprising: a face plate; a source of emitted electrons; aperture means for forming said emitted electrons into a plurality of elemental beams; first, second, and third electrode means spaced-apart along the axis of said tube between the aperture means and the face plate of the tube for accelerating said electrons; and means for focusing said electrons on a selectable portion of the face of said electric discharge tube, said focusing means being positioned adjacent said third electrode means along said axis of said tube, wherein said electrode means are positioned between said aperture means and said focusing means to accelerate said electrons through said electrode means, said first, second, and third electrode means comprising a cylinder, spiral, and cylinder respectively, and positioned in that order.
 3. The electric discharge tube as set forth in claim 2, wherein the lengths of said first, second, and third electrode means are calculated according to the relationship:
 4. The electric discharge tube as set forth in claim 2 wherein the improvement factor in reducing the length of said cathode ray tube by the use of said first, second, and third electrode means is calculated according to the relationship: where d1, d2 are the percentages of the distance of the first and second electrode means, respectively, from said aperture means to said focusing means, N is the voltage gradient from said aperture means to said focusing means, and F is the improvement factor.
 5. A cathode ray tube comprising: a face plate; a source of emitted electrons; aperture means for forming said emitted electrons into a plurality of elemental electron beams; first, second, and third electrode means spaced-apart along the axis of said tube between the aperture means and the face plate of said tube for accelerating said elemental electron beams; means for focusing said elemental electron beams on a selectable portion on the face of said cathode ray tube, said focusing means being positioned adjacent said third electrode means along said axis of sAid tube; means for individually selecting the electron beams to pass through said aperture means, wherein said electrode means are positioned between said aperture means and said focusing means to accelerate said electrons through said electrode means; said first, second, and third electrode means comprising a cylinder, spiral, and cylinder, respectively, and positioned in that order.
 6. The electric discharge tubes as set forth in claim 5 further including: mesh electrode means at the junction of said first and second electrode for reducing image aberration due to electron crossovers along the axis of said tube at predetermined electrode potentials. 